Artificial limb



March 20, 1934. w. A. MCELROY 1,951,622

ARTIFICIAL LIMB Fileduan. 7, 1931 4 sheets-sheet 1 March 2o, 1934. w. A. MCELROY. 1,951,622

ARTIFICIAL LIMB Filed Jan. 7, 1931 4 Sheets-Sheet 2 INI/ENTOR. lA//LL/A/f f4, MC 113:7

March 20, 1934. w, A. MCELROY 1,951,622

ARTIFICIAL LIMB Filed Jan. 7, 1931 4 Sheets-Sheet 3 INl/ENTOR. A MGEL reo Y March 20, 1934. w; A. McELRoY 1,951,622

ARTIFICIAL LIMB Filed Jan. 7, 1931 4 Sheets-Sheet 4 atented Mar. 20,

UNITED STATES PATENT OFFICE 2 Claims.

This invention relates particularly toganarticulated joint for artificial limbs.

An object of the invention is to provide a joint for artiiicial limbs to oscillatingly connect either f5 the foot and calf, or the calf and thigh sections, said joint permitting a point on either of two connected sections to swing in a epicycloidal arc within predetermined limits.

A further object of the invention is to provide 110 a joint for articial limbs which may be utilized either as an ankle joint or as a knee joint, the ankle joint being so constructed that movement thereof may be utilized to actuate a latch to allow the knee joint to be articulated, and the `115. knee joint being so constructed that a control cord therein may be used to swing the calf section relative to the thigh section.

Other objects and advantages are to provide an articulated joint for articial limbs that will be superior in point of simplicity, inexpensiveness of construction, positiveness of operation, and facility and convenience in use and general efficiency.

In this specification and the annexeddrawings, the invention is illustrated in the form consid- `25. ered to be the best, but it is to be understood that the invention is not limited to such form, because it may be embodied in other forms; and it is also to be understood that in and by the claims following the description, it is desired to cover the invention in whatsoever form it 4may be embodied. I

In the accompanying four sheetsl of drawings:

Fig. 1 represents a vertical crosssection through the foot and calf section of` an articial limb, 35.' having a joint therein constructed in accordance with my invention.

Fig. 2 is a plan section taken through Fig. 1 on the line 2 2.

Fig. 3 is a perspective view of an ankle joint in dissembled relation.

Fig. 4 is a side elevation of the thigh, calf and foot sections of an artificial limb, partly in cross section, having a knee joint and an ankle joint therein constructed in accordance with my invention.

Fig. 5 is a vertical section through the knee joint shown in Fig. 4, with the thigh section shown in bended position.

Fig. 6 is a side elevation of the knee joint shown in Fig. 4.

Fig. 7 is an enlarged section taken through Fig. 4, on the line 7 7.

Fig. 8 is a fragmentary plan section taken 55 through Fig. 7 on the line 8 8..

Fig; 9 isV a fragmentary plan section taken .through Fig. 7, on the line 9 9. j

Fig. 10 is an enlarged plan section taken through Fig. 4 on the line 10--10.

Fig. ll isa vertical section through the thigh, 6 0 calf, `and knee sections of an artificial limb, illustrating the knee joint connection in accordance with my invention,r and further illustrating a latch to lock the said knee joint against said articulating movement.

Fig. 12 is a side elevation of the knee joint shown in Fig. 11.

Fig. 13 is a rear view of the knee shown in Figs. 11 `and 12.

In detail the construction illustrated in the 70. drawings comprises an artificial limb formedl of a foot section 1, a calf section 2, and a thigh section 3,. The particular limb illustrated is designed ior-use on and above the knee amputation, although by suitably arranging the thigh, and calf sections, the invention might also be applied to a below the knee amputation.

Thefoot section 1, on its upper side, is provided with a recessed portion 4 to receive the lower end 5 of the cali section. A curved gear segment 6 is securely xed in the foot 1 so that the face of said segment will project above the base of the recess 4. A complementary gear segment 7 is secured in the bottom end of the cali` section 2 and projects below the plane of the bottom end of said section. The segments 6 and` 7 are adapted to mesh so that the ioot and calf sections may have a rolling or rocking movement with respect to each other. The gear segments 6 and 7 are of a width slightly less than the width 99, of the foot, as shown in Fig. 2, to give a substantial compression surface between the foot and calf sections, and to prevent any side-play or thrust between the respective sections. A slot 8V is provided through the gear segments 6` and 7 g5, substantially midway between the opposite sides thereof, and extended lengthwise of the said segments. A bushing 9` is iixed in the calf section at a point corresponding to the center of curvature of the rack 7. A similar bushing 10 isprovided in the foot section at a point approximating the center of curvature of the rack 6. The axes ofthe bushings 9 and 10 parallel each other in a horizontal plane. A shaft 11 is journaled in the bushing 9 and a similar shaft l2 is journaledin the bushing` 10. The shafts 11 and 12 are connected together by a vertically disposed. rod 13. As shown in Figs. 1 and 3, the rod 113 is securely fastenedto the shaft 11 and projectsdownwardly through an` arcuate slot 14 in the bushing 9, into and through an arcuate slot 15 in the bushing 10 permitting a threaded end of the rod 13 to be held to the shaft 12 by a nut 16. Each of the bushings 9 and 10 have a portion of their circumference cut out as at 1'?, to permit either of the shafts 11 or 12 to be withdrawn from or inserted into their respective journals. The rod 13 extends vertically between the' foot and calf sections, passing through the center slots 8 in each of the gear segments 6 and 7. Cushioning pads 18 and 19 are interposed between the matching faces of the foot and calf sections, to resist any rocking movement between the respective sections and to maintain such sections in a normal position, which will permit movement of said sections either to one side or the other of said normal position.

In operation the curved gear segments 6 and 7 function as compression members between the foot and calf sections, and the rod 13 and shafts 11 and 12 function as a tension member to hold the compression members in position to rock. When the calf section is moved in a forward direction, indicated by the arrow A, assuming the foot to be held in a stationary position, the segment 7 will rock around on the convex face of the segment 6 and at the same time the shaft 11 in the calf section, will move in a forward direction about the axis of the opposite shaft 12. When the calf section is moved in a rearward direction indicated by the arrow B, the segment 7 rocks on the segment 6 and once again the shaft 11 moves about the shaft 12 as a center. The reverse movement takes place if the calf section 2 is held in stationary position and the foot 1 is moved relatively thereto. The cushioning members 18 and 19 limit the rocking movement between the foot and calf sections, in either direction. The rocking movement between the calf and foot sections causes an oscillating movement of the shafts 11 and 12 in the journals, which is provided for by the slots through said journals.

'I have shown the compression members between the calf and foot sections as being in the form of gear segments, although it is to be understood that curved gear racks or other elements having convex peripheries in contact, might be substituted in lieu thereof. The gear segments are preferable because there is no chance of one segment slipping relative to the other and causing relative disalignment between the calf and foot sections.

If it be assumed that the foot 1 is held in a stationary position and the calf section moved relative thereto on the joint connecting said parts, any point on the calf section moves in an epicycloidal arc, said arc being of much flatter curvature than the arc on which said movable limb section would turn if it were connected to the immovable section by a conventional type of single axis bearing. The movement effected by means of the gear segments and the connecting rod therebetween, is precisely the same as that movement which occurs in certain types of planetary or epicyclic gear trains. In an epicyclic gear train, one gear is connected by a bar or rod, to a second gear which is adapted to rotate around the periphery of the rst gear, either while said first gear is stationary on its own axis, or rotating therearound. A point on the periphery of the second gear, when rotated by the first gear, in rotation therewith, prescribes an epicycloidal curve.

In the present invention only fragmentary segments of the two gears of an epicyclic gear train are utilized inasmuch as only an arc of the epicycloidal curve is necessary to accomplish the desired oscillating or rocking movement between the sections of the artificial limb.

In actual use the type of ankle joint shown in Figs. 1 and 2 gives to the user the sensation of walking on a flat surface, in contrast with the sensation of walking over an obstruction, which obtains with the conventional type of single axis ankle joint. A single axis joint of the type referred to, is illustrated in U. S. Patent No. 1,123,928 and in U. S. Patent No. 1,336,812.

In Figs. 4 through 13 inclusive, I have illustrated the application of my principle to the knee joint, or point of connection between the calf and thigh sections. The principle of operation of the joint for knee purposes is precisely the same as that where used as an ankle joint but with the exception that the knee joint is required to move throughout an arc of substantially 100, whereas the ankle joint only oscillates through an arc of never to exceed 30.

The knee joint shown in Figs. l through 10 inclusive comprises a pair of bars 20 secured on diametrically opposite upper sides of the calf section. A gear segment 21 is mounted on the upper end of each bar 20. Each segment 21 is provided with an inwardly extending bushing 22 thereon, said bushings 22 having the inner ends thereof spaced from each other. A shaft 23 ex tends through the axially aligned bushings 22 and said bars 20 to tie the assembly into a rigid unit. A cap screw 24 is adapted to engage an end of the shaft 23 to hold said shaft 23 in a set position on the said calf section.

The lower end of the thigh section 3 is provided with a pair of gear segments 25 on diametrically opposite sides thereof. A bushing 26 is provided on each of the gear segments 25 and extends inwardly therefrom. A shaft 27 has 115 its opposite ends journaled in the bushings 26.

A rod 28 has one end thereof journaled on the calf section shaft 23 between the ends of the bushings 22, and the opposite end of said rod extends through the thigh section shaft 27 and 120 the bushing 29 on said shaft. An arm 30 is mounted on the end of the shaft 28 above the bushing 29 and a nut 31 is adapted to bolt the arm 30 to the shaft 28 A pulley 32 is journaled in an end of the arm 30 and a control cord 33 125 operates around said pulley. The control cord 33 is attached to the Suspenders worn by the user of the artificial limb. An arcuate slot 34 is cut through diametrically opposite sides of the thigh section to provide a clearance space for the move ment of the shaft 23, when the thigh section is moved relatively to the calf section or vice versa. Resilient pads or bumpers 35 are provided at opposite ends of the curved slots 34 to soften the impact of the relative movement between the thigh and calf sections. The meshing portions of the gear segments 21 and 24 roll on the convex peripheries of each other and they are held in meshing contact by the connecting rod 28, which in turn is oscillated when any movement takes place between the thigh and calf sections. When the thigh section is moved relative to the calf section, or vice versa, any point on the movable section moves on an epicycloidal arc. The gear segments 21 and 25 in conjunction with their supporting shafts and the connecting rod 28, form a segmental portion of a epicyclic gear train which will function to give the desired planetary movement between the connected sections of the limb. Shoulders at the 1.5()

opposite ends of the respective gearysegments, limit` the :swinging or oscillating vmovementibetween the limb sectionsin either direction, `in

`conjunction with the resilient pads at the ends ofthe arcuate slotsheretofore described. T'I'he `control cord 33 acts through theconnecting rod 28to hold `the thigh and calf .sections of the limb in vvertical alignment. Thus, as the .calf section is swung rearward in the normal movement that takes place in walking, the control `cord V33 tends Vto throw said calf section forwardly, due to the leverage exerted on the connecting rod 28.

In Fig. 4, I have indicated a connecting cable 37 between the arm 30 and an extension of the rod 13 on the ankle joint to assist, through movement of the foot, in positioning the calf section of the limb in vertical alignment with the thigh section The thigh and calf sections may be easily disconnected by removing the set screw 24 and shaft 23 and sliding the gear segments 21 out of engagement with the opposite side bars 20.

Experiments have shown that an artificial limb equipped with a knee joint of the type shown in Figs. 4 and 5, actually causes the arc of swinging movement of the calf section to shorten about three fourths of an inch when moved from the vertical into a position at an angle to the vertical. To further emphasize this point, it can be assumed that the wearer of an articial limb can maintain the body an exact distance away from the ground level, so that the thigh section of the leg will be maintained in a xed position relatively to the said ground level. By swinging the calf section rearwardly, the arc thereof at the top of the rearward swing, would be approximately three-fourths of an inch less than when said calf section would be in alignment with the thigh section. This shortening in the radius of the swing of the calf section is due entirely to the epicycloidal curve on which the said calf section moves when swinging relatively to the thigh section. The shortening of the radius of swing of the calf section and the flattening of the curvature of the swing, permits the said calf section of the leg to be swung from a bent into a straight position with a freedom and ease that it is not possible to attain in knee joints of the single axis types heretofore referred to.

The flattening of the arc of swing of the calf section by substantially three fourths of an inch, permits the foot to clear many obstacles on the ground surface which otherwise would amount to obstructions. Particularly in knee joints of the single axis type, wherein the calf section swings on the same arc at all times, it is necessary for the user of the limb to raise the body in order to give sufficient lift to the limb to provide clearance for free movement of the foot when it is being swung from a bent to a straight position. The limp of the majority of all wearers of articial limbs, is due to the body movement necessary to lift the artificial limb sufficiently that the foot thereof will clear the surface on which the limb user is walking. The knee joint described herein, actually effects a iiattening of the arc of swing of the calf section by a distance suiiicient to clear the foot from the ground when moving it from the bent into the straight position without the necessity of any muscular movement or lift on the part of the limb wearer.

In Figs. 11, 12 and 13, I have shown a knee joint substantially the same as that described in Figs. 4 through 10 inclusive. In Figs. 1l through 13, the knee joint is shown equipped with a latch to prevent articulation of the knee joint. That `is toJsay, to'prevent'eitherithezcalf or thighsection from'beingfbentl from the vertical position sitting down, the thigh section moves `relative to the-calf section. In-eithercase, there Ais relative -movement between the thigh and calf sections,

the shaft 23 vin the said calf Vsection swinging in thearcuate slot 34 provided in the opposite sides Yof the thigh section. `In order to lock the thigh and calf sections together in a vertically aligned position, I have provided a latch member 40, pivoted intermediate its ends on the rear side of the thigh section. The forward end 41 of said latch is provided with a curve thereon adapted to rest against the horizontal shaft 23 while the outer end 42 of said latch is provided with a compression spring between it and a contiguous part of the thigh section. The compression spring 42 tends to swing the latch v40 to engage the inner end of said latch with the knee bolt, to resist the rearward thrust or swinging movement of said bolt and to hold said bolt in a relatively fixed position to maintain the thigh and calf sections in a vertically aligned position. The latch 40 is released from engagement with the knee bolt by means of a cable 43 secured at one end to the said latch, and secured at its opposite end to an extension 13 of the rod 13, which is a part of the ankle joint. As heretofore described, the rocking movement between the calf and foot sections, causes an oscillating movement of the connecting rod 13 and the ankle joint. When the heel of the foot strikes the ground, the connecting rod 13 and the extension 13 thereon, is moved in a rearward direction, indicated by the arrow C, and when the weight on the artificial limb is applied through the forward part of the foot to the ground, the connecting rod 13 and extension 13 thereon is moved in a forward direction, indicated by the arrow D. Thus, movement of the rod extension 13' forwardly within the calf section, causes a pull to be applied to the cord 43, which thereby disengages the latch 40 from the knee bolt 23, and frees the knee bolt, to permit of relative movement between the thigh and calf sections. The latch 40, through the action of the spring 42 thereon, normally lies within the path of travel or swing of the knee bolt 23 and is so designed that the knee bolt can pass the latch 40 when moving in one direction but is prevented from moving by the latch when moved in the opposite direction. The only way that the latch 40 can be released from the knee bolt, is by applying a pressure to the toe part of the foot, which will react through the ankle joint and connection through the latch, to disengage it from said knee bolt.

Although I have shown a particular form of latching mechanism known as a back check, to prevent rearward buckling of the knee joint, it is to be understood I do not wish to be limited to such form of knee buckling preventive mechanism.

Having thus described this invention, what I claim and desire to secure by Letters Patent is:

1. A joint for an articial limb consisting of related sections of a limb; a pair of curved gear racks mounted in spaced relation on the matching ends of adjacent limb sections, both pairs of racks being in meshing engagement, whereby either limb section is free to oscillate in a vertical path on a curved pitch line about a horizontal axis; means to hold the racks in meshing engagement, consisting of a shaft journaled in each section on a line parallel to the pitch line of the gear racks and connected by a vertically disposed rod secured at its opposite ends to the said shafts in the space between the pairs of meshing gear racks; an arm on one end of the rod; a control cord related to the arm to oscillate one of the limb sections; and a latch pivo'ted in one of the limb sections to look the shaft in the other limb section against arcuate movement.

2. The combination with two sections of an artificial limb, having co-acting means for rocking connection of the sections, of a sleeve trans'- versely arranged in each section in substantial parallelism, a shaft journaled in one sleeve, a rod extended from one shaft, and means to adjustably connect the rod to the other shaft to pull the sleeves and the sections toward each other to hold the said coacting means in operative position, said sleeves being apertured to allow the insertion of said shafts and rod, and to allow a limited swinging movement of the rod.

WILLAM A. MGELROY. 

